Compact variable resistor with rotary resistance element

ABSTRACT

A variable resistor which is made up of a minimum number of parts so that it can be made small in size and yet be easily assembled. Also, the variable resistor can be made as either a two terminal rheostat or a three terminal potentiometer. The variable resistor includes a hollow housing having a shaft rotatably mounted therein and projecting from a wall thereof so as to be rotatable from outside the housing. A rotor is on the shaft and has a resistance path and a contact path thereon with the contact path being electrically connected to one end of the resistor path. A pair of contacts are mounted in the housing. Each of the contacts has a terminal extending through and projecting beyond the housing, and a finger which slidably engages either the resistance path or the contact path. For a three terminal potentiometer, a second contact path is on the rotor and is electrically connected to the other end of the resistance path. A third contact is in the housing and has a terminal extending from the housing and a finger slidably engaging the second contact path.

United States Patent I Casey et al.

[54] COMPACT VARIABLE RESISTOR WITH ROTARY RESISTANCE ELEMENT [72] Inventors: Harry B. Casey, Willow Grove, Pa.; Carl E. Clark, St. Petersburg, Fla.

2,894,237 7/1959 Haynman 338/150 3,399,369 8/ l 968 Soulakis ..338/1 80 FOREIGN PATENTS OR APPLICATIONS 1,177,238 9/1964 Germany .338/150 [151 3,657,688 [451 Apr. 18, 1972 Primary Examiner-Laramie E. Askin Assistant Examiner-Gerald P. Tolin Attorney-Jacob Trachtman [57] ABSTRACT A variable resistor which is made up of a minimum number of parts so that it can be made small in size and yet be easily assembled. Also, the variable resistor can be made as either a two terminal rheostat or a three terminal potentiometer. The variable resistor includes a hollow housing having a shaft rotatably mounted therein and projecting from a wall thereof so as to be rotatable from outside the housing. A rotor is on the shaft and has a resistance path and a contact path thereon with the contact path being electrically connected to one end of the resistor path. A pair of contacts are mounted in the housing. Each of the contacts has a terminal extending through and projecting beyond the housing, and a finger which slidably engages either the resistance path or the contact path. For a three terminal potentiometer, a second contact path is on the rotor and is electrically connected to the other'end of the resistance path. A third contact is in the housing and has a terminal extending from the housing and a finger slidably engaging the second contact path.

20 Claims, 22 Drawing Figures Patented. A ril 1 1972 I 3,657,688

5 Sheets-Sheet 1 IN VENTORS HARRY 8. CA SE) CARL E. CLARK B) V \7 v Patented April 18, 1972 5 Sheets-Sheet 2 nwe/yroRs 6 I HARRY 5: CASE) i CARL 5. CLARK er \7 rromvsr Patented April 18,1972

5 Sheets-Sheet 3 INVENTORS HARRY BPCASEY CARL E. CLARK %7ORNEY Patented April 18, 1972 3,657,638

5 Sheets-Sheet 4. R

INVENTORS HARRY 8. CASE) CARL E. CLARK WJW ATTORNEY Patented April 18, 1972 3,657,688 5 Sheets-Sheet 5 l/VVE'Ni'O/PS HARRY a. user CARL E. CL ARR ArroR/vsy COMPACT VARIABLE RESISTOR WITI-I ROTARY RESISTANCE ELEMENT sistance path. A rheostat is a type of variable resistor which has a terminal connected to one end of the resistance path, and a terminal connected to the contact so as to provide a variable resistance value between the terminals as the contact moves along the resistance path. A potentiometer is a type of variable resistor having a separate terminal connected to each end of the resistance path and a terminal connected to the contact. This acts as a voltage divider to divide the voltage applied across the resistance path according to the position of the contact along the resistance path.

With the trend toward miniaturization, it has become necessary to drastically reduce the size of variable resistors, both rheostats and potentiometers. To achieve such miniaturization by merely reducing the size of previously used larger variable resistors has not been satisfactory. As the various parts of the variable resistor are reduced in size so as to reduce the overall size of the variable resistor, they become more difficult to handle and assemble. Therefore, to satisfactorily reduce the size of the variable resistors, it is necessary to redesign the variable resistor so as to minimize the number of parts of the variable resistor. By minimizing the number of parts of the variable resistor, each part can be relatively large as compared to the overall size of the variable resistor so as to permit the resistor to be easily assembled.

It is therefore an object of the present invention to provide a novel variable resistor.

It is another object of the present invention to provide a novel miniaturized variable resistor of high reliability.

It is a further object of the present invention to provide a miniaturized variable resistor composed of a minimum number of parts so as to be easy to make and assemble and can be totally enclosed and sealed.

It is still another object of the present invention to provide a miniaturized variable resistor which can be made as either a rheostat or a potentiometer.

These objects are achieved by a variable resistor which includes a housing and a rotor rotatably mounted in the housing and being rotatable from outside the housing. The rotor has a circular resistance path and a contact path thereon with the contact path being electrically connected to one end of the resistance path. A pair of contacts are mounted in the housing with one contact slidably engaging the resistance path and the other contact slidably engaging the contact path. Each contact has a terminal integral therewith with the terminals projecting from the housing. This provides a rheostat type variable resistor. For a potentiometer type variable resistor a second contact path is provided on the rotor and electrically connected to the other end of the resistance path. A third contact is'provided in the housing and slidably engages the second contact path. The third contact has a tenninal integral therewith which projects from the housing.

The foregoing and other objects of the invention will become more apparent as the following detailed description of the invention is read in conjunction with the drawings, in which:

FIG. 1 is a perspective view of one embodiment of the variable resistor of the present invention,

FIG. 2 is an exploded perspective view of the variable resistor of FIG. 1,

FIG. 3 is a top plan view of the variable resistor of FIG. 1 with the upper section of the housing removed, 7

FIG. 4 is a sectional view taken along line 4-4 of FIG. 3,

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4,

FIG. 6 is a perspective view of a modification of the variable resistor shown in FIGS. l-5,

FIG. 7 is an exploded perspective view of the variable resistor of FIG. 6,

FIG. 8 is a top plan view of the variable resistor of FIG. 6 with the upper section of the housing removed,

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8,

FIG. 10 is a perspective view of another embodiment of the variable resistor of the present invention,

FIG. 11 is an exploded perspective view of the variable resistor of FIG. 10,

FIG. 12 is a perspective view of the shaft and rotor assembly of the variable resistor of FIGS. 10 and 11,

FIG. 13 is a sectional view taken along line 13-13 of FIG. 10,

FIG. 14 is a perspective view of a modification of the variable resistor shown in FIGS. 10-13,

FIG. 15 is a sectional view taken along line l5-15 of FIG. 14,

FIGS. 16 and 17 are plan views of the opposite surfaces of the rotor of the variable resistor of FIGS. 1-5,

FIGS. 18 and 19 are plan views of the opposite surfaces of the rotor of the variable resistor of FIGS. 6-9,

FIG. 20 is a plan view of the end surface of the rotor of the variable resistor of FIGS. 10-13, and

FIGS. 21 and 22 are plan views of the opposite surfaces of the rotor of the variable resistor of FIGS. 14 and 15.

Like reference numerals designate like parts throughout the several views.

Referring initially to FIGS. 1-5, there is shown one embodiment of the variable resistor of the present invention, generally designated as 10, in the form of a rheostat. The variable resistor 10 comprises a rectangular, hollow housing 12 of an electrical insulating material, such as a plastic, having mating upper and lower sections 14 and 16 respectively. Opposed semi-cylindrical recesses 18 and 20 are provided in the mating surfaces of the front walls of the housing sections 14 and 16 respectively, and extends from the inner surface to the outer surface of the housing. The recess 20 has an enlarged diameter portion 20a adjacent the inner surface of the housing section, and the recess 18 has a mating enlarged diameter portion (not shown). A semi-cylindrical recess 22 is provided in the mating surface of the back wall of the lower housing section 16, and a mating semi-cylindrical recess (not shown) is in the mating surface of the back wall of the upper housing section 14. These mating recesses extend over only a portion of the back walls of the housing sections from the inner surface of the housing and are in axial alignment with the recesses 18 and 20 in the front wall of the housing. A notch 26 is provided in the mating surface of the front wall of the lower housing section 16 with a hole 30 extending downwardly therethrough, and a notch 28 is provided in the mating surface of the back wall of the lower housing section 16 with a hole 30 extending downwardly therethrough, and a notch 28 is provided in the mating surface of the back wall of the lower housing section 16 with a corresponding hole 32.

A rotor shaft 36 is mounted in the housing 12 with its back end being rotatably supported in the recess 22 and its mating recess, and the front end of the shaft being rotatably supported in the mating recesses 18 and 20. The front end of the shaft 36 projects from the front of the housing 12 and may be provided with an O-ring seal between the shaft and housing (not shown), and has a head 38 thereon by which the shaft can be easily rotated. A slot 40 extends across the front of the head 38 to permit the shaft to be rotated by a screwdriver or like too]. An annular flange 42 extends radially from the shaft 36 adjacent to but spaced from the head 38. The flange extends into the enlarged diameter portions of the recesses 18 and 20 and engages the wall between the two portions of the recesses 18 and 20 to prevent longitudinal movement of the shaft. The shaft 36 has a square portion 44 which is within the housing 12.

A rotor 46 is mounted on the shaft 36 within the housing 12. The rotor 46 is a flat, circular disk of an electrical insulating material, preferably one which will withstand high temperatures, such as a ceramic. The rotor 46 has a square hole 48 through the center thereof which receives the square portion 44 of the shaft 36 to prevent relative rotation between the shaft and the rotor. A snap ring 50 extends around the shaft 36 to secure the rotor 46 on the shaft. A stop lug 52 projects radially outwardly from the edge of the rotor 46. The stop lug 52 is adapted to engage the stop lug 34 of the housing 12 to limit the rotation of the rotor. An annular resistance path 54 is on one surface of the rotor 46, and extends around the surface of the rotor adjacent the periphery of the rotor (see FIG. 16). The ends 54a and 54b of the resistance path 54 are spaced apart with one end 54a being adjacent an edge of the stop lug S2 and the other end 54b being adjacent but spaced from the other edge of the stop lug 52. The resistance path 54 is a film of any resistance material coated on the surface of the rotor 46. The resistance material may be a resistance metal, mixture of metals, alloy of metals, or particles of an electrically conductive material in a glass or plastic matrix. A completely annular contact path 56 is on the other surface of the rotor 46 and extends around the rotor adjacent the periphery of the rotor (see FIG. 17). The contact path 56 is a film of an electrically conductive material coated on the surface of the rotor. A

' connecting strip 58 of an electrically conductive material is coated on the rotor and extends from the end 54a of the resistance path 54 across the edge of the rotor to the contact path 56. Thus, the contact path 56 is electrically connected in series with the resistance path 54.

A pair of metal contacts 60 and 62 are mounted in the housing 12 at opposite sides of the rotor 46. The contacts 60 and 62 have top portions 60a and 62a which fit in the notches 26 and 28 respectively in the lower housing section 16. Arcuate arms 60b and 62b extend from the top portions 60a and 62a respectively along opposite surfaces of the rotor 46. The arm 60b has a plurality of parallel fingers 600 on its end which slidably engage the resistance path 54. The arm 62b has a plurality of parallel fingers 62c in its end which slidably engage the contact path 56. Terminals 60d and 62d extend from the top portions 60a and 62a respectively through the holes 30 and 32 in the lower housing section 16 and project beyond the bottom of the housing 12. Thus, the terminals 60d and 62d are integral parts of the contacts 60 and 62.

The terminal 60d is electrically connected to the terminal 62d through the contact-60, resistance path 54, connecting strip 58, contact path 56 and contact 62. The resistance value measured across the terminals 60d and 62d is the resistance value of the portion of the resistance path 54 between the contact fingers 60c and the connecting strip 58. Rotation of the shaft 36 varies this distance so as to vary the resistance value of the rheostat 10. To assemble the variable resistor 10, the contacts 60 and 62 are mounted in the lower housing section 16 by inserting the terminals 60d and 62d through the holes 30 and 32 until the top portions 60a and 62a are seated in the notches 26 and 28 respectively. The terminals are now sealed within the lower housing section 16 by a suitable bonding technique. The rotor 46 is placed on the shaft 36 and secured thereon by the snap ring 50. The shaft and rotor assembly is then placed in the lower housing section 16 with the ends of the shaft being in the recesses 20 and 22, and the fingers 60c and 62c engage the resistance path 54 and the contact path 56 respectively. The upper housing section 14 is then placed on the lower housing section 16 and secured thereto by, for example, a suitable cement or other bonding technique. Thus, it can be seen that the variable resistor 10 is made up of a minimum number of parts so that it is easy to assemble and can be made very small in size, for example as small as 5 1 inch on each side.

Referring to FIGS. 6-9, there is shown a modification of the variable resistor 10, which modification is generally designated as 10 and is in the form of a potentiometer. Variable resistor 10' comprises a hollow housing 12' having upper and lower sections 14' and 16 which are of the same construction as the housing 12 of the variable resistor 10 previin addition to the contact receiving notches 26 and 28' in the mating surface of the front and back walls respectively, a third contact receiving notch 64 in the mating surface of the front wall which is in alignment with the notch 28' in the back wall. A hole 66 extends through the front wall of the lower housing section 16' from the notch 64 to the bottom surface of the lower housing section. A rotor shaft 36, which is of the same construction as the rotor shaft 36 of the variable resistor 10 previously described, is mounted within the housing 12'. The back end of the shaft 36' is rotatably supported in the recess 22' in the back wall of the lower housing section 16' and the mating recess in the back wall of the upper housing section 14. The front end of the shaft 36' is rotatably supported in the recesses 18' and 20' in the front walls of the housing sections.

A rotor 46 is mounted on a square portion 44 of the shaft 36 and is secured thereon by a snap ring 50'. The rotor 46' is of substantially the same construction as the rotor 46 of the variable resistor 10 previously described in that it includes an annular resistance path 54' on one surface (see FIG. 18) and an annular contact path 56' on the other surface (see FIG. 19) which is electrically connected to one end of the resistance path 54 by a connecting strip 58'. However, therotor 46' also includes a second annular contact path 68 of an electrically conductive material on the same surface of the rotor as and within the resistance path 54' (see FIG. 18). A connecting strip electrically connects the second contact path 68 with the other end of the resistance path 54'.

A pair of metal contacts 60 and 62' are mounted in the housing 12' at opposite sides of the rotor 46. The metal contacts 60 and 62' are of the same construction as the contacts 60 and 62 of the variable resistor 10 previously described. The contacts 60' and 62 are mounted in the lower housing section 16' with their top portions 600 and 62a seated in the notches 26' and 28' respectively, their terminals 60d and 62d extending through the holes 30' and 32', their an'ns 60b and 62b extending along the surfaces of the rotor, and their fingers 60c and 62c slidably engaging the resistance path 54' and the contact path 56' respectively. A third metal contact 72 is mounted in the housing 12. The third contact 72 has a top portion 72a seated in the notch 64 in the lower housing section 16', an arm 72b extending from the top portion along the surface of the rotor 46' to the second contact path 68, a pair of parallel fingers 720 on the end of the arm 72b and slidably engaging the second contact path 68, and a terminal 72d extending from the top portion 72a through the hole 66 in the lower housing section.

Thus, it can be seen that the terminal 62d is electrically connected to one end of the resistance path54' through the contact 62', the contact path 56 and the connecting strip 58'. The terminal 72d is electrically connected to the other end of the resistance path 54' through the contact 72, the second contact path 68 and the connecting strip 70. The terminal 60d is electrically connected to various points along the resistance path 54 through the contact 60. By connecting the terminals 62d and 72d across a voltage source, various voltages can be obtained between the terminal 60d and either of the other terminals by rotating the shaft 36. The potentiometer 10' is assembled in the same manner as the rheostat 10 previously described with the addition of inserting the third contact 72.

Referring to FIGS. 10-13, another embodiment of the variable resistor of the present invention, which is in the form of a rheostat, is generally designated as 100. Variable resistor comprises a housing of an electrical insulating material, such as a plastic. The housing 110 comprises a rectangular, hollow front section 112 having an open back and a back section 114 which fits across the open back of the front section. The front section 112 has a circular hole 116 through the center of its front wall, a stop lug 118 projecting from the inner surface of a wall, and a pair of spaced notches 122a and 122b in the back edge of its bottom wall. A hub 124 projects from the inner surface of the backsection 114. The hub 124 ously described. However, the lower housing section 16' has 75 has a groove 125 extending angularly thereacross.

A rotor shaft 126 is within the housing 110 with the front end of the shaft extending through and rotatably supported in the hole 116 in the front housing section 112 and an O-ring may also be used for sealing. A slot 128 extends across the front end surface of the shaft 126 and is adapted to receive a screwdriver or like tool for rotating the shaft. A stop lug 129 projects radially from the shaft 126 within the housing 110. The stop lug 129 is adapted to engage the stop lug 118 on the housing 110 so as to limit the rotation of the shaft 126 to slightly less than one revolution in either direction.

A rotor 130 is mounted on or is an integral part of the back end of the shaft 126 within the housing 110. The rotor 130 is a flat, circular disk of an electrical insulating material, preferably a material which will withstand high temperatures, such as a ceramic. An annular resistance path 132 having spaced ends is provided on the back surface of the rotor 130 around the periphery of the back surface (see FIG. The resistance path 132 is a film of any suitable resistance material coated on the surface of the rotor. A circular contact path 134 is provided on the back surface of the rotor 130 within the resistance path 132. The contact path 134 is a film of an electrically conductive material coated on the surface of the rotor. A connecting strip 136 of an electrically conductive material connects the contact path 134 to one end of the resistance path 132. The hub 124 on the back housing section 114 is of a length to engage the back surface of the rotor 130 so as to hold the shaft 126 in position in the hole 1 16 in the front housing section 112 and prevent longitudinal movement of the shaft.

A pair of metal strip contacts 138 and 140 are mounted in the housing 110 between the rotor 130 and the back housing section 114. The contacts 138 and 140 have arms 138a and 140a respectively extending downwardly and angularly away from their top ends, and a pair of parallel fingers 138k and 14% respectively on the ends of the arms. Terminals 138C and 1400 extend downwardly from the bottom ends of the contacts 138 and 140 respectively. The contact 138 is positioned at one side of the hub 124 with the fingers 138b slidably engaging the resistance path 132 and the terminal 138C extending through the notch 122a in the front housing section 112 and projecting beyond the bottom of the housing 110. The contact 140 is seated in the groove 125 in the hub 124 with the fingers 1 40b slidably engaging the contact path 134 and the terminal 1400 extending through the notch 122b in the front housing section 112 and projecting beyond the bottom of the housing 110.

The terminal 1386 is electrically connected to the terminal 1400 through the contact 138, resistance path 132, connecting strip 136, contact path 134 and contact 140. The resistance value measured across the terminals 1380 and l40c is the resistance value of the portion of the resistance path 132 between the contact fingers 138k and the connecting strip 136. Rotation of the shaft 126 varies this distance so as to vary the resistance value of the variable resistor 100. To assemble the variable resistor 100, the shaft 126 and rotor 130 assembly is inserted in the front housing section 112 with the front end of the shaft extending through the hole 116. The terminals 138 and 140 are placed in position in the notches 122a and 122b in the front housing section 112, and the back housing section 114 is placed across the back open side of the front housing section 112 and the sections are secured together and the terminal sealed to the housing by suitable techniques. Thus, it can be seen that the variable resistor 100 is made up of a minimum number of parts so that it is easy to assemble and can be made very small in size.

Referring to FIGS. 14 and 15, there is shown a modification of the variable resistor 100, which modification is generally designated as 100' and is in the form of a potentiometer. The variable resistor 100' comprises a housing 110' having a front section 112' and a back section 114' which are of the same construction as the housing sections 112 and 114 of the variable resistor 100 previously described. However, the front housing section 112 has a hole 142 extending through its bottom wall adjacent the inner surface of the front wall thereof and adjacent one of the side walls. A shaft 126' is mounted in the housing 110 with the front end of the shaft 126 extending through and rotatably supported in a hole 116' in the front wall of the front housing section 112'. The shaft 126' is of the same construction as the shaft 126 of the variable resistor previously described. A rotor 130' is mounted on the back end of the shaft 126' within the housing The rotor is of the same construction as the rotor 130 of the variable resistor 100 previously described but with the addition of a second contact path 144 of an electrically conductive material on the front surface of the rotor 130 and extending annularly around the surface at the peripheral edge thereof (see FIG. 21). A connecting strip 145 of an electrically conducting material extends from the second contact path 144 across the edge of the rotor 130' to the other end of the resistance path 132'. Thus, the contact paths 134' and 144 are electrically connected to opposite ends of the resistance path 132', (see FIG. 22).

A pair of contacts 138' and 140' are within the housing 1 10' between the rotor 130' and the back housing section 114'. The contacts 138' and 140' are of the same construction as and are mounted in the housing in the same manner as the contacts 138 and 140 of the variable resistor 100 previously described. Thus, the contact fingers of the contacts 138' and 140' slidably engage the resistance path 132' and the contact path 134' respectively, and the terminals 1380' and 1400' project from the bottom of the housing 110. A third contact 146 is within the housing 110' between the rotor 130' and the front wall of the front housing section 112'. The contact 146 has a pair of parallel fingers at its top which slidably engage the second contact path 144, and a terminal 146b at its lower end. The terminal 146b extends through the hole 142 in the front housing section 112' and projects beyond the bottom of the housing 110'.

Thus, the terminal 146b is electrically connected to one end of the resistance path 132 through the contact 146, contact path 144 and connecting strip 145. The terminal 1400' is electrically connected to the other end of the resistance path 132' through the contact 140', contact path 134' and connecting strip 136'. The terminal 138C is electrically connected to vari ous points along the resistance path 132' through the contact 138. By connecting the tenninals 146b and 1400' across a voltage source, various voltages can be obtained between the terminal 138a and either of the other terminals by rotating the shaft 126'. The variable resistor 100' is assembled in the same manner as the variable resistor 100 previously described with the addition of inserting the contact 146 into the front housing section 112' prior to inserting the shaft and rotor assembly.

Thus, there is provided by the present invention variable resistors which are made up of a minimum number of parts so that they can be made very small in size yet can be easily assembled. In addition, the variable resistors can be made either as a two terminal rheostat or as a three terminal potentiometer.

What is claimed is:

1. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts having a finger and a terminal, the finger of one of said contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; the housing including a hollow front section having a front wall and a bottom wall and being open at its back, and a back section which extends across the back of the front section and is secured thereto, the front wall of the front section having a hole therethrough through which the front end of the shaft extends, the bottom wall having a pair of spaced notches in its back edge through which the terminals extend, the slots being open to the rear of the front section and being enclosed by the back section, the back section retaining and positioning the rotor and contacts within the housing with the contacts in engagement with their respective paths of the rotor, whereby the resistor can be assembled by placing the shaft with said rotor mounted thereon in the hollow front section with the shaft extending through the hole thereof, positioning the contacts in the notches with the fingers engaging their respective paths of the rotor and securing the back section with the front section of the housing.

2. A variable resistor in accordance with claim 1 in which the rotor is a flat circular disk secured to the back end of the shaft, the resistance path is on the surface of the rotor facing the back section of the housing, the contact path is on the same surface of the rotor as the resistance path, and the contacts are mounted between the rotor and the back section of the housing.

3. A variable resistor in accordance with claim 2 including a second contact path of an electrically conductive material on the rotor and electrically connected to the other end of the resistance path, and a third contact mounted in said housing, said third contact having a finger at one end slidably engaging the second contact path and a terminal at its other end extending through and projecting beyond the housing.

4. A variable resistor in accordance with claim 3 in which said rotor has a pair of flat surfaces and the second contact path is on the surface of the rotor opposite to that on which the resistance path is provided, and the third contact is between the front wall of the front housing secton and the rotor.

5. A variable resistor in accordance with claim 4 in which the second contact path is electrically connected to the other end of the resistance path by a connecting strip of an electrically conductive material which extends from the second contact path across the peripheral edge of the rotor to the other end of the resistance path.

6. A variable resistor in accordance with claim 2 in which the resistance path extends around the periphery of the said surface of the rotor and the contact path is within the resistance path.

7. A variable resistor in accordance with claim 6 in which the contact path is electrically connected to one end of the resistance path by a connecting strip of an electrically conductive material on said surface of the rotor. v

8. A variable resistor in accordance with claim 7 including a hub projecting from the inner surface of the back secton of the housing and engaging the rotor so as to prevent longitudinal movement of the shaft and rotor.

9. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the-housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to and end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts having a finger and a terminal, the finger of one of said contacts slidably engaging the resistance path, the finger through which the front end of the shaft extends; the rotor being a flat circular disk secured to the back end of the shafi, the resistance path being on the surface of the rotor facing the back section of the housing, the contact path being on the same surface of the rotor as the resistance path, and the contacts being mounted between the rotor and the back section of the housing; the resistance path extending around the periphery of the said surface of the rotor and the contact path being within the resistance path; the contact path being electrically connected to one end of the resistance path by a connecting strip of an electrically conductive material on said surface of the rotor; and including a hub projecting from the inner surface of the back section of the housing and engaging the rotor so as to prevent longitudinal movement of the shaft and rotor; the hub having a groove extending angularly thereacross, the one contact being positioned at one side of said hub with the finger of the one contact slidably engaging the resistance path, and the other contact being within said groove with its finger slidably engaging the contact path.

10. A variable resistor in accordance with claim 9 inwhich the housing is rectangular and the terminals of the contact extend through and project beyond the bottom of the housing.

11. A variable resistor in accordance with claim 10 including a stop lug on the interior of the housing and a stop lug on the rotor which is adapted to engage the housing stop lug to limit the degree of rotation of the shaft. 7

12. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; and a pair of metal contacts mounted in said housing, each of said con- 1 tacts having a finger and a terminal, the finger of one of said of the other contact slidably engaging the contact path, and

contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; the rotor being a flat circular disk mounted on the shaft with the resistance path being on one surface of the rotor and the contact path being on the other surface of the rotor, and the contacts are at opposite sides of the rotor; said housing comprising mating upper and lower sections each having front and rear walls,'the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the contacts are supported between mating surfaces of the housing sections, whereby the resistor can be assembled by mounting the contacts in a section of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts.

13. A variable resistor in accordance with claim 12 in which each of said contacts comprises a top section, an arm extending from one end of the top section, the finger being on the end of the arm and the terminal extending from the other end of the top section.

14. A variable resistor in accordance with claim 13 in which the top section of one of the contacts is seated between the mating surfaces of the front walls of the housing sections with the terminal of the one contact extending through a hole in the front wall of the lower housing section, and the top section of the other contact is seated between the mating surfaces of the back walls of the housing sections with the terminal of the other contact extending through a hole in the back wall of the front wall of the front section having a hole therethrough lower housing section.

15. A variable resistor in accdnfance with claim 14 in which the mating surface of each of the front and back walls of the lower housing section has a notch therein in which the top section of the respective contact is seated.

16. A variable resistor in accordance with claim 15 in which the housing has a stop lug projecting from its inner surface, and the rotor has a stop lug projecting radially from its outer contact path being on the same surface of the rotor as the resistance path and being electrically connected to the reedge which is adapted to engage the housing stop lug to limit.

the degree of rotation of the shaft.

17. A variable resistor comprising a hollow housing; a shaft rotatably supported insaid housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a first contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; a second contact path of an electrically conductive material connected to the other end of the resistance path; and first, second and third metal contacts each comprising a one piece metal strip mounted in said housing, each of said contacts having an intermediate portion with a finger at one end and a terminal at the other end, the finger of one of said contacts slidably engaging the resistance path, the fingers of the other contacts respectively slidably engaging the first and second contact paths, and the terminals extending through and projecting beyond said housing; said housing comprising mating upper and lower sections providing recesses therebetween and each having front and rear walls, the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the intermediate portions of the contacts are supported in respective recesses between mating surfaces of the housing sections, whereby the resistor can be assembled by mounting the contacts in respective recesses of a section of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts.

18. A variable resistor in accordance with claim 17 in which the second contact path is on the same surface of the rotor as the resistance path and is electrically connected to the resistance path by a connecting strip of an electrically conductive material.

19. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a fiat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a first contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; a second contact path of an electrically conductive material connected to the other end of the resistance path; the second sistance path by a connecting strip of an electrically conductive material; and first, second and third metal contacts each comprising a one piece metal strip mounted in said housing, each of said contacts having a finger at one end and a terminal at the other end, the finger of one of said contacts slidably engaging the resistance path, the fingers of the other contacts respectively slidably engaging the first and second contact paths, and the terminals extending through and projecting beyond said housing; said housing comgrising mating upper and lower sections each having front an rear walls, e ront end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the contacts are supported between mating surfaces of the housing sections, the contacts each including a top section seated between the mating surfaces of the housing section, an arm extending from one end of the top section, the fingers being on theend of the arm, and the terminal being at the other end of the top section and extending through a hole in the lower housing section; whereby the resistor can be assembled by mounting the contacts in a secton of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts.

20. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts having an intermediate portion with a finger at one end and a terminal at the other end, the finger of one of said contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; said housing comprising mating upper and lower sections providing recesses therebetween and each having front and rear walls, the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the intermediate portions of the contacts are supported in respective recesses between mating surfaces of the housing sections, whereby the resistor can be assembled by mounting the contacts in respective recesses of a section of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts. 

1. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts having a finger aNd a terminal, the finger of one of said contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; the housing including a hollow front section having a front wall and a bottom wall and being open at its back, and a back section which extends across the back of the front section and is secured thereto, the front wall of the front section having a hole therethrough through which the front end of the shaft extends, the bottom wall having a pair of spaced notches in its back edge through which the terminals extend, the slots being open to the rear of the front section and being enclosed by the back section, the back section retaining and positioning the rotor and contacts within the housing with the contacts in engagement with their respective paths of the rotor, whereby the resistor can be assembled by placing the shaft with said rotor mounted thereon in the hollow front section with the shaft extending through the hole thereof, positioning the contacts in the notches with the fingers engaging their respective paths of the rotor and securing the back section with the front section of the housing.
 2. A variable resistor in accordance with claim 1 in which the rotor is a flat circular disk secured to the back end of the shaft, the resistance path is on the surface of the rotor facing the back section of the housing, the contact path is on the same surface of the rotor as the resistance path, and the contacts are mounted between the rotor and the back section of the housing.
 3. A variable resistor in accordance with claim 2 including a second contact path of an electrically conductive material on the rotor and electrically connected to the other end of the resistance path, and a third contact mounted in said housing, said third contact having a finger at one end slidably engaging the second contact path and a terminal at its other end extending through and projecting beyond the housing.
 4. A variable resistor in accordance with claim 3 in which said rotor has a pair of flat surfaces and the second contact path is on the surface of the rotor opposite to that on which the resistance path is provided, and the third contact is between the front wall of the front housing secton and the rotor.
 5. A variable resistor in accordance with claim 4 in which the second contact path is electrically connected to the other end of the resistance path by a connecting strip of an electrically conductive material which extends from the second contact path across the peripheral edge of the rotor to the other end of the resistance path.
 6. A variable resistor in accordance with claim 2 in which the resistance path extends around the periphery of the said surface of the rotor and the contact path is within the resistance path.
 7. A variable resistor in accordance with claim 6 in which the contact path is electrically connected to one end of the resistance path by a connecting strip of an electrically conductive material on said surface of the rotor.
 8. A variable resistor in accordance with claim 7 including a hub projecting from the inner surface of the back secton of the housing and engaging the rotor so as to prevent longitudinal movement of the shaft and rotor.
 9. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to and end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts haviNg a finger and a terminal, the finger of one of said contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; the contacts being a one piece metal strip with the finger being at one end and the terminal at the other end; the housing including a hollow front secton having a front wall and being open at its back, and a back secton which extends across the back of the front section and is secured thereto, the front wall of the front section having a hole therethrough through which the front end of the shaft extends; the rotor being a flat circular disk secured to the back end of the shaft, the resistance path being on the surface of the rotor facing the back section of the housing, the contact path being on the same surface of the rotor as the resistance path, and the contacts being mounted between the rotor and the back section of the housing; the resistance path extending around the periphery of the said surface of the rotor and the contact path being within the resistance path; the contact path being electrically connected to one end of the resistance path by a connecting strip of an electrically conductive material on said surface of the rotor; and including a hub projecting from the inner surface of the back section of the housing and engaging the rotor so as to prevent longitudinal movement of the shaft and rotor; the hub having a groove extending angularly thereacross, the one contact being positioned at one side of said hub with the finger of the one contact slidably engaging the resistance path, and the other contact being within said groove with its finger slidably engaging the contact path.
 10. A variable resistor in accordance with claim 9 in which the housing is rectangular and the terminals of the contact extend through and project beyond the bottom of the housing.
 11. A variable resistor in accordance with claim 10 including a stop lug on the interior of the housing and a stop lug on the rotor which is adapted to engage the housing stop lug to limit the degree of rotation of the shaft.
 12. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts having a finger and a terminal, the finger of one of said contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; the rotor being a flat circular disk mounted on the shaft with the resistance path being on one surface of the rotor and the contact path being on the other surface of the rotor, and the contacts are at opposite sides of the rotor; said housing comprising mating upper and lower sections each having front and rear walls, the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the contacts are supported between mating surfaces of the housing sections, whereby the resistor can be assembled by mounting the contacts in a section of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the uppEr and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts.
 13. A variable resistor in accordance with claim 12 in which each of said contacts comprises a top section, an arm extending from one end of the top section, the finger being on the end of the arm and the terminal extending from the other end of the top section.
 14. A variable resistor in accordance with claim 13 in which the top section of one of the contacts is seated between the mating surfaces of the front walls of the housing sections with the terminal of the one contact extending through a hole in the front wall of the lower housing section, and the top section of the other contact is seated between the mating surfaces of the back walls of the housing sections with the terminal of the other contact extending through a hole in the back wall of the lower housing section.
 15. A variable resistor in accordance with claim 14 in which the mating surface of each of the front and back walls of the lower housing section has a notch therein in which the top section of the respective contact is seated.
 16. A variable resistor in accordance with claim 15 in which the housing has a stop lug projecting from its inner surface, and the rotor has a stop lug projecting radially from its outer edge which is adapted to engage the housing stop lug to limit the degree of rotation of the shaft.
 17. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a first contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; a second contact path of an electrically conductive material connected to the other end of the resistance path; and first, second and third metal contacts each comprising a one piece metal strip mounted in said housing, each of said contacts having an intermediate portion with a finger at one end and a terminal at the other end, the finger of one of said contacts slidably engaging the resistance path, the fingers of the other contacts respectively slidably engaging the first and second contact paths, and the terminals extending through and projecting beyond said housing; said housing comprising mating upper and lower sections providing recesses therebetween and each having front and rear walls, the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the intermediate portions of the contacts are supported in respective recesses between mating surfaces of the housing sections, whereby the resistor can be assembled by mounting the contacts in respective recesses of a section of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts.
 18. A variable resistor in accordance with claim 17 in which the second contact path is on the same surface of the rotor as the resistance path and is electrically connected to the resistance path by a connecting strip of an electrically conductive material.
 19. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessAble for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a first contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; a second contact path of an electrically conductive material connected to the other end of the resistance path; the second contact path being on the same surface of the rotor as the resistance path and being electrically connected to the resistance path by a connecting strip of an electrically conductive material; and first, second and third metal contacts each comprising a one piece metal strip mounted in said housing, each of said contacts having a finger at one end and a terminal at the other end, the finger of one of said contacts slidably engaging the resistance path, the fingers of the other contacts respectively slidably engaging the first and second contact paths, and the terminals extending through and projecting beyond said housing; said housing comprising mating upper and lower sections each having front and rear walls, the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the contacts are supported between mating surfaces of the housing sections, the contacts each including a top section seated between the mating surfaces of the housing section, an arm extending from one end of the top section, the fingers being on the end of the arm, and the terminal being at the other end of the top section and extending through a hole in the lower housing section; whereby the resistor can be assembled by mounting the contacts in a secton of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts.
 20. A variable resistor comprising a hollow housing; a shaft rotatably supported in said housing with one end of said shaft extending through said housing to be accessable for rotation from outside the housing; a rotor within said housing and mounted on said shaft to rotate with said shaft, said rotor having a flat surface; an annular resistance path of an electrical resistance material on the surface of said rotor, said resistance path having spaced apart ends; a contact path of an electrically conductive material on the surface of said rotor and electrically connected to an end of said resistance path; and a pair of metal contacts mounted in said housing, each of said contacts having an intermediate portion with a finger at one end and a terminal at the other end, the finger of one of said contacts slidably engaging the resistance path, the finger of the other contact slidably engaging the contact path, and the terminals extending through and projecting beyond said housing; said housing comprising mating upper and lower sections providing recesses therebetween and each having front and rear walls, the front end of the shaft extending through and being rotatably supported in mating recesses in the front walls of the housing sections and the back end of the shaft being rotatably supported in mating recesses in the back walls of the housing sections while the intermediate portions of the contacts are supported in respective recesses between mating surfaces of the housing sections, whereby the resistor can be assembled by mounting the contacts in respective recesses of a section of the housing, placing the front and rear ends of the shaft in the front and rear recesses of the section of the housing with the rotor mounted on the shaft and engaging the contacts, and securing together the upper and lower sections for rotatably retaining said shaft with the housing and the rotor within the housing in engagement with the contacts. 